Production of alpha-naphthol by catalytic reduction of alphatetralol and alpha-tetralone



Patented May 6, 1952 OFFICE .PRODUCTION OF ALPHA-NAPHTHOL BY CATALYTIC REDUCTION OF ALPHA- .TETRIALOL AND ALPHA TETRAlxONE Robert Johnson, Ingomar, Pa., assignor to Koprpers Company, :Inc., Pittsburgh, Pa.,a corporation of Delaware ;N.o Drawing. Application January 9,1948, Serial No. 1,490

4 Claims.

This invention relates to the manufacture of alpha-naphthol. More particularly, the invention relates to the catalytic dehydrogenation of a-tetralol'or a mixture of -a-tetralone and a-tetra lolto produce alphaenaphth'ol.

French patent, 693,596 of November 12, 1930, describes a process of producing alpha-naphthol by reacting a-tetra'lone with su'lphurby a reaction which sets free hydrogen sulphide (H2S). In accordance with the present lllV8l1fiOUa-tetralone or a-tetralol or a mixture of these compounds may be directly dehydrogenated to producealpha-naphthol.

Iii-my copend-ing applications, Serial No. "655,- 773 fil'ed March 20, 1 946, nowU. S.'Patent'N0. 2,454,804, issued November 30, I948, and Serial No. 656,782, filed March 23, 1946, now U. 8. Patent No. 2,462,103, issued-February 22, 1949, processesare described for the manufacture of a-tetralol and wtetralone respectively from tetralin. In each of these processes, both-u-tetra- 101 and e-tetralone are formed as intermediate products and the mixture is further refined to separate the products.

The manufacture of a-tetralol 0112: I maybe .briefiy described as -,'follows: 'Tetraiin is oxidized. withair at a temperature of 180 to 120 C. inliquid phase and in therpresence .01 copper carbonate asa. catalyst. Bylthis reaction 'tetralin peroxide is .formed and this peroxide in the tetralinis then converted to a mixture of a-ltetralol and a-tetralone, by heating the mixture to a temperature oi'6'0" to 120' with an aqueous sodium hydroxide solution. .The tetralin \solution of a-tetralol and a-tetralone is practically insoluble in the caustic solution and may .be seption :reaction product by vacuum distillation :or subatmospheric pressure distillation.

.The manufacture of a-tietralone may be briefily described as follows: Tetralin risoxidized with air at90 Grin the liquid'phase and in'the presence of suspended'coppericarbonateto give a concentrated solution of tetralin peroxide in tetralin. The peroxide solution res-ultingfrom oxidation is then treated with'ia hot'aqueous solution "of" copper sulfate to convert the peroxide principally to alpha tetralone. As 'statedin the last patent listed above, one mayyin general, employ for this treatment a copper salt 'of a mineral acid stable'under .the operating conditions which include temperatures between 25 and 100 ,C. and preferably between and C. Only a small "amount of alpha ,tetralol is formed in decomposition of tetralin peroxide-with this agent. The 'tetralin solution of -tetralone and -tetralol is practically insoluble "in the aqueous solution and maybe separated bysuitable means as ,by decantation. 'Then-tetralol and a-tetralone mixture, after separation from tetra'lin by distillation, is vaporized and contacted 'withactivated alumina to .c'onvertfthe eitetralolto di hydronaphthalene. The .alpha-tetralone unaifected by this treatment may be readily separated from dihydronaphthalene by distillation. Reference is made to the abovementioned patent applications for detailed description. of the above-mentioned processes.

I have discovered that both alpliarti tral 'and alpha-tetralone may-be simultaneously dehyd ogenated to .form ,alpha-naphthol. Accordingly the mixture of ,a-tetralol and a-tetralone'ebtainejd as products of oxidation may be used asv such withoutthe necessity "for ajsep'arate separation step. I

My .work has jfurther shown thatjthe' alpha: tetralone may be more efiectiyel'y and econdnii cally ,dehydrogenateid than alpha tetralol. Therefore the process of oxidation of tetralin'i's carried out toiproduce the maximum amount of a-tetralone and this oxidation .productpreferably becomes the raw material for producing the alpha-tetralol. In my work I have shown that I am able to make by the above-mentioned process mixtures of alpha-tetralone and alpha-tetralol in which the alpha-tetralone varies from 40% to 90% and the alpha-tetralol varies from 60% to The primary object of the present invention is to provide a process of producing alpha-naphthol from a mixture of alpha-tetralol and alphatetralone.

Another object of the invention is to provide a cheap and efficient process for producing alphanaphthol from tetralin. a

A further object of the invention is to provide a process of producing alpha-naphthol by catalytic dehydrogenation of alpha-tetralol and/or alpha-tetralone.

With these and other objects in view the invention consists in the process of producing alpha-naphthol as hereinafter described and particularly defined in the claims.

The manufacture of alpha-tetralone in accordance with the preferred form of the process preferably consists in the dehydrogenation of a mixtureof alpha-tetralone and alpha-tetralol in which the percentage of alpha-tetralone is greater than 50% of the mixture. Accordingly the process of making alpha-tetralone as outlined above is preferred for making the mixture of alpha-tetralone"""and alpha-tetralol. This mixture is pumped at a constant rate through an externally heated tube'which is filled with catalyst generally in a granular form .that is packed within the tube. Acomparatively long tube with catalyst therein is used because it has been found that the space velocity, or time of reaction preferably should be greater than 0.5 second'and good results have been obtained when using 2.0 seconds. The a-tetralone and a-tetralol are dehydrogenated in vapor phase wherein the temperature in the cracking zonemay vary between 500 C. and 650 C. The time of reaction andthe temperature depend upon the type of' catalyst being used. If calcined granular limestone is used as a catalyst in combination with steam, a vapor mixture of.a-tctralol and c-tetralone may be eifectively dehydrogenated at a temperature of 650 C. to give a conversion of 30% to 35% alpha-naphthol per pass.

L The limestone used was preferably alimestone obtained in western Pennsylvania which .is-calcined at'a low temperature. Such a limestone contains. from 50% to 60% of CaOand 1% to 2% of F8203. A ferruginous limestone containing approximately 86% CaO and 14% F6203 is a very effective dehydrogenation catalyst. A dolomite made .up of 19%. F6203, 48% (321.0, 33% MgO when calcined is an effective dehydrogenation catalyst which may be used with steam for the dehydrogenationof'a vapor mixture of a-tetralol and a-tetralone.

- The alpha-naphthol that is produced by the catalytic dehydrogenation reaction may be separated from the reaction mixture by caustic soda.

, .When using limestone as a catalyst and a temperature of 650 C. with steam and amixture of tetralol and tetralone in the ratio of 10:1, a conversion to alpha-naphthol'of 33.5% per pass with an ultimate yield value of 72% was obtained. The limestone catalyst does not become poisoned in this reaction and is therefore well adapted for the dehydrogenation reaction. The charging stock was a mixture of 51% a-tetralone and 47%a-tetralol. The products of the reac tio'n in'addition to" alpha-naphthol were dihy dronaphthalene 11.6% and a mixture of a-tetralol and a-tetralone of 53.5%. This intermediate reaction product consisted of approximately 33.5% a-tetralol and 65.5% a-tetralone.

The use of limestone as a catalyst is very desirable even when operating at temperatures of 600 to 650 C. because the activity of the catalyst is not interfered with by the deposition of carbon thereon. When using lime (i. e., calcined limestone) as a catalyst it is desirable to use a charging stock having a large amount of .a-tetralone because a-tetralone is not dehydrogenated to form dihydronaphthalene as readily as is the a-tetralol.

A large number of runs have been made with many different types of catalyst using a mixture of a-tetralone and a-tetralol as charging stock.

' It has. been found that an economic charging stock which may be readily dehydrogenated cat'alytically with limestone at a temperature of 600 to 650 0. consists of approximately 60% a-tetraione and 40% a-tetralol. When this mix ture is dehydrogenated, a conversion of 30% to 35% per pass of alpha-naphthol is obtained and by recycling the unconverted a-tetralone-tetralol residue an ultimate yield of 80 to' may be obtained.

Preferably the catalytic dehydrogenation of the mixture-of a-tetralone and a-tetralol is carried out at atmospheric pressure, although higher yields of alpha-naphthol may be obtained if the catalytic reaction is carried out in a vacuum or subatmospheric pressure.

The reaction mixture from the catalytic dehydrogenation of alpha-tetralol and tetralone is preferably refined by distilling the mixture. In the distillation alpha-naphthol is the first to come overhead and thereafter dihydronaphthalene may be recovered and then a mixture of e-tetralol and a-tetralone may be recovered as a separate distillate. This distillate can be mixed with the feed stock for recycling back to the process. In the reaction, part of the c-tetralcne and a-tetralol mixture will be recycled from three to six times before it is converted to alpha naphthol or intermediate products. Y

The preferred form of the invention having been thusdescribed, what is claimed as new is:

1. In the production of alpha-naphthoL the method which comprises converting alpha-tetralone into products containing at least 80 percent of alpha-naphthol, based on the amount of alpha-tetralone converted, by contacting vapors of alpha-tetralonewith calcined limestone at a temperature in the range between 500 and-650 C. for a time in the range between 0.5 to two seconds and in the presence of steam.

2.,In the production of alpha-naphthol, the method which comprises converting a mixture of. alpha-tetralone and alpha-tetralol into products containing at least 80 percent alpha-naphthol, based on the amount of said mixture converted, by contacting said mixture in the vapor state with a calcined limestone at a temperature in the range between 500? and 650 C. for a time;

in the, range between 0.5 and two seconds and in the presence of steam.

3. The method of claim 2 in which thevaporous mixture contains predominantly alphat'etralone.

g 4. A process of making alpha-naphthol from solution containing a copper salt of amineral' acid stablgunder operating conditions including a tempe "ture in the range of 60 to 90 C. to

decompos on products comprising a. mixture of Q temperat 'ire in the range between 500 and 650 C. for a time in the range between 0.5 and two'fw seconds and in the presence of steam.

ROBERT JOHNSON.

REFERENCES CITED The following references are of record in the 15 file of this patent:

6 UNITED STATES PATENTS Number Name Date 2,242,325 Read May 20, 1941 2,291,585 Bartlett etal July 28, 1942 2,418,879 Haslam Apr. 15, 1947 2,444,035 Corso-n etal. June 29, 1948 OTHER REFERENCES Linstead et a1, "Dehydrogenation. Part III. The Formation Of Naphthols J. Chem. Soc., 1940, pages 1134-1139 ('G pages) 

1. IN THE PRODUCTION OF ALPHA-NAPHTHOL, THE METHOD WHICH COMPRISES CONVERTING ALPHA-TETRALONE INTO PRODUCTS CONTAINING AT LEAST 80 PERCENT OF ALPHA-NAPHTHOL, BASED ON THE AMOUNT OF ALPHA-TETRALONE CONVERTED, BY CONTACTING VAPORS OF ALPHA-TETRALONE WITH CALCINED LIMESTONE AT A TEMPERATURE IN THE RANGE BETWEEN 500* AND 650* C. FOR A TIME IN THE RANGE BETWEEN 0.5 TO TWO SECONDS AND IN THE PRESENCE OF STEAM. 